The objectives of this proposal are to study the relationship of the renin-angiotensin-aldosterone system to the kallikrein-kinin system. We have developed a stable autoperfused kidney preparation. We propose the infusion of various peptides, including angiotensins I, II, and III, tetra and tridecapeptide renin substrates, vasopressin, renin, and bradykinin into the preparation, with subsequent measurement of plasma and urine osmolality, Na ion and K ion, urinary kallikrein and kinins, GFR, renal blood flow and renal kallikrein. We have determined that tetra and tridecapeptide renin substrates, angiotensin I, and a analogue of vasopressin are inhibitory to urine kallikrein estrase activity. We will determine if they also inhibit binding of kallikrein-kallikrein antibody. Methods are being developed for determination of renal tissue kallikrein, and we propose development of a bradykinin immunoassay.